Praise be to Allah the Lord of the Worlds.
Coupons and vouchers issued by advertising and marketing companies, or tour and travel operators or some trading centers come in different forms:
First: They are of real value, sold for a certain price and enable the bearer to benefit from services and commodities with similar value. There is nothing wrong with buying this type and benefitting from it.
Second: They include a certain discount on the commodities and services of certain companies and are bought against a certain sum of money. This type is prohibited since it involves Gharar (Risk/uncertainty) as the bearer takes the risk of collecting less or more than the value of the amount that he had already paid for the coupons or he gets nothing at all. This type was banned in resolution (138) of the Jordanian Iftaa` Council and (103) of the International Islamic Fiqh Academy of the Muslim World League.
Third: They include a discount on the prices of commodities and services, but they are given to people free of charge. There is nothing wrong with benefitting from this type since it is similar to a pledged donation.
In conclusion, the aforementioned question indicates that those coupons include a certain discount and are sold for a certain amount of money, thus it isn`t permissible to purchase them. And Allah the Almighty knows best.